I have a 72x18x26 and I have 7 silver dollars in it, an ornate, a lap and a palmas bichir, a lima shovelnose, a common pleco and a striped raphael. Currently there are also 2 jewels that will soon be warming the lima's belly. I have 2 fx5s and a wet/dry running it. There are no problems currently, althoughI think it will be overstocked when they all get full grown (by then I hope to have a 240gal). The silver dollars have grown well in the month or two that I have had them, they are 4-5" and I bought them at 3-4".
I handle the feeding differential by feeding flakes and small floating pellets first and then putting in the pellets and frozen. That slows the silver dollar's feeding frenzy a little.